British lawmakers have called on the government to curb the "threat" of internet giants to the U.K.'s public service broadcasters (PSBs).

The Guardian newspaper published a letter Friday to Jeremy Wright, the U.K. minister for digital, culture, media and sport, in which a group of nine cross-party politicians warned that if action was not taken "the enormous power of the global internet giants is going to sweep traditional PSB television away."

The signatories of the letter accused internet giants like Netflix and Amazon of "finding ways to circumvent" rules introduced by the 2003 Communications Act, a law that sought to protect British PSBs. They argued that this was being done in various ways, including the building of smart TVs with a Netflix button and burying PSB programs in digital on-demand platforms.

"If we keep allowing them to be pushed out and viewers pushed towards global pay TV services, the PSBs will not be able to (sustained) and we will lose the content that has defined so much of this country for the best part of a century," the letter said. "If the situation is bad now it will only get worse as new TV services are launched by other internet giants. We cannot afford a delay.

"We urge you: recognize the threat and help Ofcom to act to preserve our precious PSBs."

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Ofcom, Britain's broadcasting regulator, closed a consultation on the matter of protecting the U.K.'s PSBs in October. It said that new legislation was needed if the U.K. Parliament wanted to keep PSBs easy to find amid the growth in internet television services.

The lawmakers behind the letter — which coincided with the birthdays of the BBC and Britain's Channel 4 — called on him to give the matter parliamentary time, indicating that such legislation could be put on the agenda for debate.

A spokesperson for the Department for Digital, Culture, Media and Sport said: "Ofcom are due to report by 2020 on whether we need to strengthen linear prominence and whether we need to extend prominence to on-demand. If Ofcom makes clear that there is a problem that needs fixing with legislation, government will look at bringing that forward."

Spokespersons for Netflix and Amazon were not immediately available for comment when contacted by CNBC.